The invention relates to a method for transporting bulk material, granular material or powdery material through a conveyor line from an inlet, where the powdery material is forced into the line by means of a pressurized gaseous medium, to an outlet, wherein several supply elements are connected to the conveyor line between said inlet and said outlet for the purpose of introducing additional pressurized gaseous medium into the conveyor line.
A method of this kind can be derived from U.S. Pat. No. 5,240,355.
With the device which is described and depicted in said U.S. patent, the conveyor line is subdivided into a number of sections, to each of which a number of supply elements are connected. The adjustment of each supply element must be carried out by hand, whereby the individual supply elements may be adjusted differently from each other. In addition to that, depending on the operating conditions, the adjustment of the supply elements which are connected to each section can be changed simultaneously for all of said supply elements, whilst maintaining the possible differences in the adjustment of the individual supply elements.
From European patent No. 0 446 520 a device for feeding several burners with powdery coal is known, wherein a mixture of air and powdery coal is supplied to each burner via a separate pipe. It is intended thereby to supply an identical amount of powdery coal per unit time to each burner via the various pipes. The flow value of the mixture of coal and air is measured in a first pipe portion for the purpose of controlling the flow in a pipe. Furthermore, the flow value of the air is measured in a pipe portion further downstream. On the basis of these two measurements, which are carried out at locations some distance apart in the pipe, pressurized air is led into the upstream portion of the pipe.
German patent application No. 2,412,142 furthermore discloses a device for transporting powdery material via a line, into which air can be blown through a number of spaced-apart injectors. The introduction of air into the line via the injectors can be controlled by means of a control programme, for example in order to effect a pulsating transport of the material through the conveyor line. Means for measuring the velocity in the pipe are not shown or described in said patent application.
German patent application No. 1,900,355 discloses a device for transporting spaced-apart balls of material through a pipe. Valves are thereby connected to the pipe in regularly spaced-apart relationship, via which valves pressurized air can be introduced into the pipe. The movement of the balls of material through the pipe is detected by light boxes disposed near said valves, via which the valves are controlled. Pressure gauges are furthermore provided near the connections of the valves to the pipes, by means of which the supply of air to the valves can be influenced. A similar device is described in German patent application No. 1,781,025.
The object of the invention is to provide a method of the above kind, wherein the transport of the material through the conveyor line can be automatically controlled in an optimum manner during operation.
According to the invention this can be achieved in that the velocity of the material through the conveyor line is measured near the connection of each supply element for introducing additional pressurized gaseous medium into the conveyor line, and in that the introduction of pressurized gaseous medium via the respective supply element is automatically controlled in dependence on the velocity that is detected.
The use of the method according to the invention makes it possible to achieve an optimum control of the transport of the material. The adjustment of the supply elements can be automatically adapted thereby to different types of material having different physical properties, which are to be transported through the same conveyor line. Also changes in the path to be followed through the pipe system, for example if several outlets must be reached, will not affect the optimum manner in which the material is being transported and/or necessitate outside interference by the user of the device.
The method according to the invention can be carried out efficiently by using a device comprising a conveyor line which is provided with an inlet, with an outlet, and with supply elements connected to said conveyor line between said inlet and said outlet, which supply elements function to introduce additional pressurized gaseous medium into the conveyor line, wherein according to the invention a measuring element for measuring the velocity of the material through the conveyor line is disposed near the connection of each supply element to the conveyor line, and wherein means for adjusting the supply element in dependence on the velocity of the material through the conveyor line that has been detected by means of said measuring element are provided between the supply element and the measuring element in question.
It is noted that the gaseous medium may be air or a suitable gas.